What does bothering to read some distributed systems literature have to do with demanding unnecessary perfection? Did NATS have in their docs that JetStream accepted split brain conditions as a reality, or that metadata corruption could silently delete a topic? You could maybe argue the fsync default was a tradeoff, though I think it’s a bad one (not the existence of the flag, just the default being “false”). The rest are not the kind of bugs you expect to see in a 5 year old persistence layer.

Exactly, "losing data from acknowledged writes" is not failing to be perfect, it's failing to deliver on the (advertised) basics of storing your data.